How Hormones Affect Metabolism and Food Intake

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Have you ever wondered what the secret is to the so-called yo-yo dieting? Why do people after losing weight, not only regain it but even add extra kilos? Are obese people really that hungry? Although our food choices and the daily intake are influenced by a number of factors (organoleptic features of food we eat, eating habits, lifestyle, food advertising, etc.) our body is capable of achieving a harmonious balance between the satiety hormones and hormones that stimulate appetite and food cravings. These hormones are produced in our adipose tissue, pancreas and gastrointestinal tract and then travel to our hypothalamus, brain stem and the vegetative nervous system where they send a signal to feel hungry…  So far, scientists have identified about 20 different hormones that affect our food intake, satiety and metabolism, but most widely discussed among them are insulin, leptin, ghrelin and cortisol.

Insulin

After a meal, the pancreas secretes large amounts of the hormone insulin into the bloodstream enabling the body tissues -especially the muscles, liver and adipose tissue – to either use glucose for energy or store it for future use. The insulin acts like a key, allowing glucose to flow from the bloodstream into body’s cells.

One of the most important effects of insulin is to stimulate the liver to store glucose in the form of glycogen. That way between meals, when the blood glucose levels drop, the glycogen will be converted back into glucose and slowly released into the bloodstream to maintain normal glucose balance.

Insulin, however, has many other effects on our body: It affects fat storage in the body by increasing glucose utilization in the tissues. This will in turn reduce fat utilization. Insulin also promotes the synthesis of fatty acids in liver and fat cells, as well as promotes the formation of proteins in the body and prevents their degradation. Now, you may wonder why it is so important to maintain glucose level in the blood when there are plenty of other „resources” that can provide us with energy? The answer to this is simple; the brain, the retina, and some tissues rely on glucose as their main source of energy and require continuous delivery of glucose from blood.

Leptin

Leptin is also called „satiety hormone“ and it is produced in our adipose tissue. After leptin enters the bloodstream, it reaches the hypothalamus and tells our brain that we have enough energy stored in our body. But if we are on a calorie-restricted diet, we are eating  less and our fat cells are losing fat. This will cause a decrease in leptin levels and our brain will start feeling hungry. In return, we will want to eat more and the more food we eat, the more energy is being stored in adipose tissue, helping leptin levels to be re-established.  Studies have confirmed that overweight people have large amounts of leptin in their bodies, but their brains aren’t getting the signal to stop eating. As our body thinks there is not enough energy stored, we will feel uncontrolled hunger and tend to overeat. This lack of sensitivity to the hormone is called leptin resistance.

 

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Ghrelin

Ghrelin is a peptide hormone that is most commonly produced in the stomach but is also present in other tissues. This hormone stimulates food intake and indicates metabolic changes that lead to body mass/fat increase.  Ghrelin levels increase before a meal and decrease after food intake. Ghrelin stimulates the formation of gastric acid in the stomach, stomach activity and the functioning of the pancreas. It is believed that the very high level of this hormone is responsible for the strong hunger people feel after a period of food deprivation. Research has shown that because of ghrelin, foods high in calories, like hamburgers, chocolate, pizza, etc., are a lot more attractive than low-calorie food such as fruits or vegetables. The high level of ghrelin causes uncontrollable hunger and overeating. Also, some studies have shown that the usual drop in ghrelin level after a meal is less present in some conditions such as metabolic syndrome, diabetes, or obesity. But the effect of this hormone is not limited to metabolism and gastrointestinal tract. Ghrelin also reduces blood pressure and is important for reproductive health, the immune system and, according to some studies, it plays an important role in learning processes and memory.

Cortisol

Cortisol is a steroid hormone synthesized in the adrenal gland and is responsible for maintaining optimal glucose levels in the blood. It also regulates blood pressure and maintains the health of the blood vessels.  Cortisol is also involved in inflammatory processes in the body and the metabolism of fats, carbohydrates and proteins. This hormone is also known as “stress hormone” because its secretion is intensified in the fight-or-flight mechanism.  Small amounts of cortisol in the bloodstream have a positive effect, such as reduced feelings of pain, memory enhancement and increased energy. It is believed that this hormone helps the body to cope with traumatic and stressful situations and extreme environmental conditions. However, high levels of this hormone (for example, when a person is constantly exposed to stressful situations), can cause unwanted health issues such as increased blood pressure, decreased immunity, inflammatory reactions, increased glucose levels, which then can cause insulin resistance, degradation of bones, the accumulation of adipose tissue in the abdominal area…

It’s all about balance

In a healthy organism, all the hormones in the body are in balance. And each hormone has an impact on other specific hormones in the body. Therefore, if a hormone is not in balance it will affect the hormonal balance of the entire body.

For example, if a person would experience a stressful situation for a longer period of time, the level of cortisol in the blood will be elevated. As a result, the level of insulin will also be raised. This hormonal imbalance can lead to obesity, type 2 diabetes, and a number of other illnesses.

So how to avoid the vicious cycle of hormonal disbalance? How to deal with a low-level of leptin and a high level of ghrelin when dieting?

  • Learn some relaxation techniques to reduce the negative effects of stress. Meditate, practice yoga, exercise… Find something that’s right for you.
  • Research has shown that listening to relaxing music reduces the level of cortisol in the blood
  • Eat regularly several smaller meals a day. This will prevent eating a large amount of food in one or two meals (and increased insulin levels). Also, regular smaller meals will maintain a stable concentration of ghrelin.
  • Eat wholegrain cereals and whole grain products. Also, keep in mind the GI (glycemic index) of food. The glycemic index is an indicator of the intensity and the rate at which your body converts carbohydrates from food into glucose. Foods with a high glycemic index cause a sudden increase of glucose in the blood, resulting in increased insulin levels.
  • Sleep enough. Insufficient sleep affects negatively the secretion of ghrelin and leptin, which leads to increased food intake.
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